Increase the iocount on a vnode, checking that the vnode is alive and has not changed vid (i.e. been recycled)
- macOS 10.4+
0 for success, ENOENT if the vnode is dead, in the process of being reclaimed, or has been recycled and reused.
If vnode_getwithvid() succeeds, the resulting io-reference must be dropped with vnode_put(). This function succeeds unless the vnode in question is dead, in the process of dying, or has been recycled (and given a different vnode id). The intended usage is that a vnode is stored and its vid (vnode_vid(vp)) recorded while an iocount is held (example: a filesystem hash). The iocount is then dropped, and time passes (perhaps locks are dropped and picked back up). Subsequently, vnode_getwithvid() is called to get an iocount, but we are alerted if the vnode has been recycled.
On success, vnode_getwithvid() returns with an iocount held on the vnode; this type of reference is intended to be held only for short periods of time (e.g. across a function call) and provides a strong guarantee about the life of the vnode. vnodes with positive iocounts cannot be recycled. An iocount is required for any operation on a vnode.